The source said the change could come as soon as Wednesday. It's yet another escalation in the clash between California and Trump administration. Industry watchers feared that the Trump administration's plan to freeze federal emission standards, a rollback of tightened standards created by the Obama administration, could have led to two auto markets in the US
-- one subject to more restrictive California regulations and another linked to significantly less stringent federal standards.
The Trump administration has also made unraveling Obama's environmental legacy a priority. Months after he arrived in office, President Donald Trump announced the US would leave the Paris Climate Agreement and in June he revoked the Clean Power Plan, the key regulation underpinning the US' pledge in the landmark 2015 international agreement. The administration also recently revoked Obama's Waters of the United States rule and has made number of other moves that would allow for increased oil and gas production on public lands.
The source said the Trump administration will find the EPA previously acted unlawfully by granting the state a waiver from the Clean Air Act and allowing it to develop stricter standards than those of the federal government. About a dozen states have adopted California's standards, which are geared toward the larger goal of curbing greenhouse gases.
California has historically been allowed to have stricter emission standards due to the state's unique geography and history of intense air pollution, highlighted by the thick smog that once blanketed Southern California. Revoking the Golden State's ability to set its own standards could stymie the downward trend in California's air pollution.
California Gov. Gavin Newsom, a Democrat, said in a statement that the Trump administration "has abdicated its responsibility to the rest of the world on cutting emissions and fighting global warming" and is acting "on a political vendetta."
"It's a move that could have devastating consequences for our kids' health and the air we breathe, if California were to roll over," Newsom said. "But we will not -- we will fight this latest attempt and defend our clean car standards."
Separately, California Attorney General Xavier Becerra said Trump could not pull the waiver.
"While the White House clings to the past, automakers and American families embrace cleaner cars," Becerra said in a statement.
"It's time to remove your blinders, President Trump, and acknowledge that the only person standing in the way of progress is you. You have no basis and no authority to pull this waiver. We're ready to fight for a future that you seem unable to comprehend; we'll see you in court if you stand in our way," he added."
The EPA did not immediately respond to requests for comment on Tuesday afternoon.
President Donald Trump is visiting California as part of his travels this week. The EPA is expected to make the announcement in Washington, D.C.
Talks between the Trump administration and the California Air Resources Board broke down earlier this year
, and the White House announced it would move forward with replacing the Obama-era federal standards.
Faced with that, California regulators negotiated a voluntary standard with four major automakers. Those negotiations are now the subject of
a Justice Department antitrust investigation.